50 COMPARATIVE ANATOMY OF 



body, that only the wrists and hands appear ; and 

 they are thus so short that they can scarcely be ad- 

 vanced forwards at all. But what they lose in ex- 

 tent they gain in power. They are peculiarly con- 

 structed for swimming, and serve also for seizing or 

 holding. The animal has the power of presenting 

 to the water either the edge or the flat part of the 

 paw ; and it can moreover either approximate its 

 fingers, which have an intervening membrane, and 

 so are webbed, or it can separate them, so as to di- 

 minish or augment the surface of this oar or paddle, 

 as it has been called. The hind-legs are still more 

 modified. From the knee downwards they are 

 placed not at right angles, but in a line parallel with 

 the body. The thigh-bone is very short, and is so 

 bent that its lower portion at the knee is anterior. 

 The legs have in this way very little power of mo- 

 tion, the foot alone enjoying it ; and that with great 

 facility and power, especially in bending and ex- 

 tending itself upon the leg, thus removing it from, 

 or approximating it to, the mesial line. One effect 

 of this arrangement is very apparent, viz. that the 

 posterior extremities, thus altered, are thereby much 

 assimilated to the broad horizontal tail of the Whale 

 tribe ; and that the Phocidae are thus, like them, 

 enabled to dart towards the surface of the ocean for 

 breath, and with a rapidity which otherwise they 

 never could have attained. In all the species, 

 the fingers can readily be distinguished through the 

 paw ; and in most the nails appear at the termi- 

 nation of the member. In one group, however, 



